1. Field of the Invention
The present invention pertains to the programming of nodes, and more particularly to the programming of nodes by the use of electronic methods and hardware.
2. Description of Related Art
The prior art discloses a number of references which teach methods for addressing devices along a communications link. U.S. Pat. No. 4,232,294 to Burke et al. discloses a method and apparatus for rotating priorities between stations sharing a communications channel. Each station is provided with a different time delay by a cyclic counter so that conflicts within the channel are minimized. These time delays determine which station receives control of the bus and can be rotated to give every station equal access. U.S. Pat. No. 4,437,157 to Witalka et al. discloses a dynamic subchannel allocation process. A means is provided to store a particular arrangement of nodes in a register. This register can be altered at any time to change an allocation scheme. U.S. Pat. No. 4,646,236 to Crockett et al. discloses a pipelined control apparatus having a means to initialize a system which uses a software routine. Once reset, the system can be reconfigured to any set-up.
In typical electrical mechanical devices, hundreds of wires can be necessary to electrically connect electrical loads, e.g. motors, solenoids, sensors, switches etc., with a control mechanism. Identical programmable modules which interface with electrical loads along a bus can relieve the need for an excess of interconnecting wires and an excess of unique fixed address modules. FIG. 1 illustrates programmable modules (e.g. modules 20-1 and 20-2) located along bus 12. Module 20-1 is connected to DC motor 70A, solenoid 72A, microswitch 75 and sensor 76. Module, 20-2 is connected to DC motor 70B, solenoid 72B, indicator 77 and push button switch 78. The modules are programmed to receive signals from the loads and to send signals to the loads. For example, module 20-1 may receive a signal from bus 12 which is relayed to DC motor 70A and from sensor 76 which is relayed to another module located along bus 12. In such a manner, the modules located along bus 12 perform input and output operations.
In U.S. Pat. Nos. 5,044,964 and 5,037,308, programming of identical programmable modules (i.e. the programming of the input nodes of the IC chip of the modules) is undertaken by mechanical means. This mechanical programming is accomplished by puncturing or breaking printed wiring board (PWB) runs or by pulling down or grounding programming fingers which connect to the inputs of the IC chip of a module. Both types of mechanical programming are inexpensive, but the first procedure of breaking the PWB runs results in a device which cannot be reprogrammed while the second method requires the fingers to be pulled up or down for reprogramming. In either case, human intervention for programming is necessitated.
Therefore, a need exists for a system which makes possible the electronic programming of address and configuration information to a plurality of input/output connector modules located along a time multiplex bus, the system allowing the electronic programming and reprogramming of any number of modules located along the bus.